The present invention relates to a disk head assembly for supporting read/write heads adjacent rotating disks in a disk drive and more particularly, to a baseplate for attaching a head suspension assembly to a head actuator arm.
In hard disk drives data are stored on magnetizable surfaces of a plurality of rotatable disks that are mounted in a coaxial stack on a housing of the drive. Transducer heads that write data to and read data from the disk surfaces are supported by an actuator that is mounted on the housing and can be actuated to position the transducer heads in alignment with concentric data tracks defined on the disks. Each transducer head is attached to one end of a head suspension that is connected to an actuator arm that extends from the actuator body. The suspensions include a flexible load beam constructed of light steel sheet that has a bend formed in it. The load beam acts as a spring that forces the head against the disk surface with an accurate pre-load or xe2x80x9cgram loadxe2x80x9d. Air turbulence caused by the rotating disks lifts the heads slightly off the disks so that the heads fly on an air bearing across the disk surfaces. The air bearing force is counteracted by the suspension gram load.
A head-carrying suspension is attached to an actuator arm using a baseplate that forms a part of the head suspension. The baseplate includes a flat flange portion and cylindrical hub portion or boss. The baseplate hub is passed through a load beam clearance hole and the flange is spot welded to the load beam. The combined baseplate, load beam and a flexure make up a head suspension, and the suspension has the hub of the baseplate extending through and beyond the load beam clearance hole.
The hubs of two suspensions are inserted into an actuator arm boss hole formed through an actuator arm extending from an actuator body, one hub entering an actuator arm boss hole from each end of the hole. A swage ball is passed through the cylindrical hubs to force the peripheries of the hubs to expand (swage) into tight engagement with the inner peripheries of the actuator arm boss hole. Thus, an actuator arm may carry two suspensions on opposite sides thereof to support two transducer heads in opposing directions, one up and one down.
A typical baseplate has two primary regions, flange region and a hub region. The flange region is a flat portion to which the load beam is welded. This area preferably remains flat and free from distortion so that it serves as a stable mounting feature for the load beam and ideally remains so throughout the swaging operation. The hub region is an extended boss whose upper end is contiguous with the flange portion and whose lower end passes through boss clearance holes in both the load beam and the actuator arm. The hub region supplies the retention torque between the baseplate, which is welded to the load beam, and the actuator arm by plastically expanding and cold working during the swaging operation, creating a press fit with the actuator arm.
U.S. Pat. No. 6,128,164 issued to Rishi Kant et al. on Oct. 3, 2000 discloses a disk drive having a head-gimbal assembly (HGA) which is attached to an actuator arm of an actuator assembly. The HGA includes a read/write head, a flexure, and a suspension arm. The suspension arm has a first end including the flexure supporting the read/write head, and a second end including a hole having an attached swaging member extending through it. The swaging member includes a baseplate and a swaging boss which interface at an annulus region. A circular hole is formed through a top surface of the baseplate and extends downward partially through the swaging member. A non-circular hole, concentric with the circular hole, is formed through a bottom surface of the swaging boss, and extends upward partially through the swaging member. The non-circular hole has a smaller diameter than the circular hole. The shape of the non-circular hole may be any geometric shape such as a two-lobed swaging hole, a three-lobed swaging hole, an elliptical hole or a hexagonal hole. The swage boss of the swaging member is inserted into an opening in the actuator arm. A compatible non-circular key, which is a rod of the same configuration and size as the non-circular hole, is inserted through the hole and non-circular hole in the swaging member. The non-circular key is held at both ends by a fixture and turned so that the non-circular bole is deformed. The swage boss expands in size to form a tight interface fit with the actuator arm. The plastic deformation of the swaging member is located at an interface region between the baseplate and the swaging boss.
U.S. Pat. No. 6,046,885 issued to Kim Aimonetti et al. on Apr. 4, 2000 discloses a baseplate having a hub, a flange having an outer flange region at an outer periphery of the flange that is contiguous with the hub. The flange has a modified region that at least partially surrounds and is contiguous with the clamping region, the modified region having a stress reducing configuration such that the clamping region is thicker than the outer flange region. The modified region may be a circular or linear step, and can be on either side of the flange. The step fits the contour of a load beam and the flange is welded to the load beam. The load beam thickness is the same as or less than the thickness of the step.
In the prior art, a problem with this process is that the baseplate flange becomes warped by stress from the hub during the swaging operation. Consequently, the load beam, which is welded to the baseplate flange, is deformed by the warping of the baseplate flange, adversely affecting the gram load on the transducer head and the retention torque between the baseplate and arm.
The problems of gram load variation and retention torque loose result from the fact that connection part between the flange region and hub region is too strong.
It is, therefore, desirable to provide an actuator arm assembly for a magnetic disk unit in which the baseplate flange region almost frees from distortion and the hub region plastically expands larger during a swaging operation so that the gram load change will be smaller and the retention torque between the baseplate will be larger.
Therefore, an object of the present invention is to provide a baseplate for an arm and suspension assembly.
A further object of the present invention is to provide an arm and suspension assembly which is equipped with the baseplate.
A still further object of the present invention is to provide a hard disk drive which is equipped with the arm and suspension assembly
A baseplate in accordance with the present invention comprises a cylindrical hub, a flat flange and a circular notch formed in said flange.
A circular notch at the connection part between the flange region and hub region can make the hub region easily plastically expanded and flange region almost free from distortion.
During a swaging operation with notched baseplate, the deformation of baseplate flange region will be smaller and that of the hub region will be larger. Thus smaller gram load change and larger retention torque will be got.